Rail sleeper

ABSTRACT

The rail sleeper ( 10 ) is provided with a sleeper body ( 12 ) comprising one rail contact area ( 16 ) on each of the opposing ends thereof, within which the sleeper body ( 12 ) is widened. A rail ( 24 ) may be fixed in each rail contact area ( 16 ) by means of a hold-down element ( 28 ) able to grip a rail foot. Each rail contact area ( 16 ) comprises three rail contact surfaces ( 18 ) adjacent to one another in the extension of the rail ( 24 ). At least one hold-down element ( 28 ) is disposed between and above at least one partial region of respective adjacent rail contact surfaces ( 18 ) of each rail contact area ( 16 ). The sleeper body ( 12 ) is free of reinforcement elements within each rail contact area ( 16 ) on both sides of the intermediate spaces between adjacent rail contact surfaces ( 18 ).

The present invention relates to a rail sleeper as used in the laying of rails and tracks.

In the field of railroad construction, rail sleepers made of wood, concrete, steel and plastic material are known. Further, rail sleepers are known in the most various forms, such as e.g. monoblock sleepers, bi-block sleepers and Y-sleepers. Further known are various fastening systems, these being e.g. rib-plate fasteners, Pandrol fasteners or fasteners with angled guide plates.

Rail sleepers normally comprise, on their ends, rail contact areas where the rails are fixed on their rail feet with the aid of hold-down elements. To allow for an increased amount of horizontal forces to be taken up in the horizontal direction along the extension of the rail sleepers (i.e. transversely to the extension of the rails), it is known to broaden the width of the rail contact areas. Examples of such rail sleepers are found in DE-A-100 23 389, DE-A-27 35 797, DE-A-21 55 479, U.S. Pat. No. 1,555,662 and U.S. Pat. No. 1,406,454.

It is an object of the invention to improve the support and fixation of rails on rail sleepers having widened rail contact areas.

According to the invention, to achieve the above object, there is proposed a rail sleeper provided with

-   -   a sleeper body comprising respectively a rail contact area on         each of the opposing ends thereof and having an enlarged width         within said rail contact areas,     -   each rail contact area being adapted for fixation of a rail         therein by means of a hold-down element able to grip a rail         foot.

In this rail sleeper, it is according to the invention provided

-   -   that each rail contact area comprises three rail contact         surfaces arranged adjacent to one another in the extension of         the rail,     -   that at least one hold-down element is arranged between and         above at least one partial region of respective adjacent rail         contact surfaces of each rail contact area, and     -   that the sleeper body is free of reinforcement elements within         each rail contact area on both sides of the intermediate spaces         between adjacent rail contact surfaces.

Thus, according to the invention, each widened rail contact area comprises three rail contacts surfaces arranged adjacent to each other in the extension of the rail. Said three rail contacts surfaces are formed e.g. as plane surfaces arranged in a common plane and being raised relative to their environment. The rail supported on said rail contact surfaces is arranged to bridge the intermediate spaces between adjacent rail contact surfaces. According to the invention, it is further provided that the hold-down elements are arranged to the effect that they are positioned above the region between respectively two adjacent rail contact surfaces and extend beyond these rail contact surfaces. In this manner, on the respective end of the sleeper body, the rail feet are reliably held down onto the respective three rail contact surfaces, the rail foot resting with plane and areal contact on all of said rail contact surfaces. This in turn is advantageous for taking up horizontal forces acting transversely to the rail. Further, according to the invention, the hold-down elements can be arranged and fixed in “staggered” positions relative to the rail contact surfaces because, in these regions, no reinforcement (armoring) elements are arranged in the sleeper body on both sides of the intermediate spaces between adjacent rail contact surfaces. Such reinforcement elements are employed for clamping or reinforcing the sleeper body, especially when concrete is used.

Alternatively, two or more hold-down elements can be provided per group of rail contact surfaces. If the hold-down elements are realized in the form of per se known spring clamps, their fastening screws can be positioned laterally of the intermediate space between respectively two adjacent rail contact surfaces. However, at these sites, also other hold-down elements attachable by screws can be connected to the sleeper body by means of the screws. In case that four hold-down elements are used for each group of three rail contact surfaces, respectively two hold-down elements will be arranged opposite to each other. If only two hold-down elements are used, these will be arranged diagonally opposite to each other.

Within its widened rail contact areas, the sleeper body has a relatively larger extension transversely to its longitudinal extension. To make it possible to stabilize the resultant laterally projecting areas of the sleeper body, it is suitable to provide respectively at least one first reinforcement profile element below the rail contact areas within the sleeper body. This reinforcement profile element is suitably arranged substantially centrally relative to the rail axis; in case that, for each rail contact area, use is made of a plural number of reinforcement profile elements, which then will preferably extend parallel to each other, these plural reinforcement profile elements are arranged symmetrically and centrally relative to the rail axis.

A quite good reinforcement of the widened rail contact areas can be realized by forming the reinforcement profile element as a profile comprising a leg extending substantially at a right angle to the rail contact surface. Thus, for instance, the reinforcement profile element can be realized as an angular profile, T-profile or U-profile. These types of profiles will lend a high stability and reinforcement to the rail contact areas and respectively to the sleeper body within its rail contact areas.

It is particularly useful to configure the sleeper body as a bi-block sleeper body. Thereby, the entire rail sleeper will take up horizontal forces to a higher degree and will dissipate them into the ballast bed. In a bi-block sleeper, it is provided by the invention or an advantageous embodiment of the invention that the two blocks are connected to each other by a second reinforcement profile element. Said second reinforcement profile element in turn is connected to the first reinforcement profile elements. Thus, the bi-block sleeper comprises a reinforcement framework consisting of the second reinforcement profile element and the two first reinforcement profile elements extending transversely thereto at the ends of the first reinforcement profile element, wherein the intersecting/connecting points of the reinforcement profile elements are arranged below the middle rail contact surfaces. This applies also if the sleeper body is formed as a monoblock and comprises the at least one second reinforcement profile element.

Suitable materials for the sleeper body are e.g. concrete and polymer concrete. Due to the use of reinforcement profile elements below the widened rail contact areas and the second reinforcement profile element between the two blocks of a rail sleeper of the bi-block sleeper type, it is suitable to produce the two blocks from plastic. Generally, in this regard, any type of plastic and particularly also recycled plastic, is useful. The plastic blocks should be able to move relative to said reinforcement framework consisting of the second reinforcement profile element and the first reinforcement profile elements since plastic has a higher temperature coefficient than metal, which is used for the reinforcements. In so far, it is of advantage if the reinforcement profiles (longitudinal and/or reinforcement profile elements) have smooth surfaces which allow the plastic to “slide” thereon during its expansion or its contraction after expansion. The first reinforcement profile elements, since they are arranged centrically relative to the rails, will effect a centering of the rail contact areas so that these cannot be displaced transversely to the rails. The reinforcement profile elements, having legs preferably extending at right angles to the rail contact areas, provide for a fixation of the rail contact areas, which in a plastic sleeper are made of plastic, at sites below the rail feet.

According to an advantageous embodiment of the invention, it is further provided that, in a bi-block sleeper, the second reinforcement profile element between the two blocks is protected from corrosion. For this purpose, an embodiment of the invention provides that the region of the second reinforcement profile element that is located between the two blocks is surrounded and respectively filled with a plastic foam, preferably a PU foam. This foam has the advantage that, in case of an expansion of the blocks if these are made of plastic, it will yield and respectively follow the temperature-induced movement of the blocks. Further, a receiving groove or recess can be formed in the foam above the rails sleeper so as to accommodate a conductor rail which for safety reasons is prescribed for train control on routes admitted for higher speeds.

The invention will be explained in greater detail hereunder by way of several embodiments and with reference to the drawing. In the various Figures of the drawing, the following is shown:

FIG. 1 is a plan view of an embodiment of a rail sleeper according to the invention in bi-block design,

FIGS. 2 and 3 illustrate alternative options for rail attachment either by use of two pairs of hold-down elements or by use of only two hold-down elements per rail,

FIGS. 4 to 7 are perspective partial views of the reinforcement framework of the rail sleeper,

FIG. 8 is a plan view of the rail sleeper provided with plastic foam arranged between the blocks and surrounding the reinforcement structure, and

FIG. 9 is a cross-sectional view taken along the line IX-IX in FIG. 8.

The rail sleeper according to the invention will be described hereunder in the context of its realization as a bi-block sleeper made of plastic. As a material, preferred use is made of recycled plastic. Recycled plastic is available in very larger quantities and is best suited for this use. Further, such plastic can be optimally integrated into a material cycle, which is highly environmentally friendly.

This cycle will take the following development:

Plastic waste→sleeper production from the waste materials→separation of materials at the end of the useful life of the sleeper→new production of sleepers from the same materials→plastic waste→sleeper production from the waste materials→separation of materials at the end of the useful life of the sleeper→new production of sleepers from the same materials→etc. Of course, the recycled plastic recovered from the old sleeper can also be used for other applications.

The bi-block connection is realized e.g. by an angle iron, a T-profile, a tube profile or a double-I profile. However, also other materials can be used for the connection, such as e.g. Carbon, GFK, Keflar etc. The rail sleepers can be produced with an individual total length of e.g. 2.25 m, 2.40 m, 2.60 m or with other desired lengths for a wide variety of rail tracks.

For a safe and long-lived operation of the rail tracks, it is the shape of the sleeper, the load transmission surface to the ballast, the head surface for the horizontal forces and the material for the reduction of the dynamic vibration which are of eminent relevance.

As a further important point, consideration has to given to the form of the rail support on the rail sleeper. For the economic usefulness of a track bed system, also the number of the rail sleepers per track kilometer and the number of fastening members per track kilometer are of relevance. When building a new construction, all of the above mentioned assessment criteria should be considered.

The bi-block form has been selected in order to achieve a load-free zone in the intermediate region of the tracks so that no “riding” of the rail sleepers will occur in the middle of the tracks. The connection element for the two blocks, made of steel selected from a large variety or of other materials, is each time provided to extend to a site laterally outside the contact area of the tracks and the fastening means. From this construction, it results that there exists no central fastening on the rail sleepers. This is intended to be the case. The sleeper width is derived from the opening dimension of the tamping machine. Preferably, this will result in a width of about 350 mm. The sleeper thickness should preferably be 160 mm. This is a matter of an adaptation to the large number of existing rails provided with wooden sleepers. In this manner, it is accomplished that, in case of a reconstruction of an existing rail with wooden sleepers, no lowering of the subgrade has to be performed, as would be required in case of a conversion from wooden sleepers to concrete sleepers.

-   -   Wood=160 mm     -   Concrete≈210 mm.

In this manner, considerable costs are saved.

For optimizing the contact surfaces for the rails and the surfaces for horizontal load dissipation on the ballast, the invention provides a widening of the rail sleeper under the rail. From this, there results the basic form of the rail sleeper 10 as shown in FIG. 1 of the embodiment comprising a bi-block sleeper body 12. Each of the two blocks 14 comprises a rail contact area 16 comprising the successive rail contact surfaces 18 separated from each other by interspaces 20. The widened rail contact areas 16 extend laterally beyond the blocks 14 and are reinforced by reinforcement profiles 22. These reinforcement profiles 22 are arranged centrally relative to the rails 24 (see also FIGS. 2 to 7) and are rigidly connected to the ends of a longitudinal profile 26. The longitudinal profile 26 connects the two blocks 14 of the bi-block sleeper body 12 to each other.

By said enlargement of the sleeper width under the rails, there is achieved the largest possible surface area offering resistance to the horizontal forces. A further effect of the enlargement of the sleeper width consists in a nearly continuous support of the rails. As a further advantage, this construction allows for a very favorable dual support of the rail on the sleeper as known e.g. in the Y-type steel sleeper. Said enlargement also allows for a triple support of the rail.

The arrangement of the reinforcement profiles 22 under the rails 24 offers a manifold possibility for rail attachment, as shown in FIGS. 2 and 3. FIG. 2 illustrates the situation wherein, per rail 24 and sleeper block 14, respectively two pairs of hold-down elements 28 are provided (formed as spring clamps in the present embodiment). Said hold-down elements 28 grip around the rails 24 on the feet of the latter, notably above the interspaces 20 between the rail contact surfaces 18. In the configuration according to FIG. 3, there are provided, for each rail 24, two hold-down elements 28 arranged on both sides of a rail 24 and connecting different rail contact surfaces 18 to each other and, respectively, being arranged above the interspaces 20 between respective different adjacent rail contact surfaces 18. One of the essential aspects of the invention is to be seen in said two variants of the rail attachment by hold-down elements 28 gripping around respective adjacent rail contact surfaces 18, as depicted in FIGS. 2 and 3, in combination with said widened rail contact area 16 comprising three rail contact surfaces 18 serially arranged in the direction of the rail.

The creep resistance of the rails is largely determined by the amount of the clamping forces in the rail attachment structures because these clamping forces will result in the frictional forces between rail and sleeper. This creep resistance is of particular relevance for

-   -   mountain routes with narrow radii,     -   for taking up braking forces (such as e.g. of an eddy-current         brake)     -   for the continuous welding of radii, and     -   for the securing of fracture gaps in case of rail fracture.

By this type of rail sleeper construction, a very large contact area is accomplished. This makes it possible to provide

-   -   a dual attachment in offset configuration per sleeper head         (FIG. 3) or     -   a quadruple attachment per sleeper head (FIG. 2).

These different attachment types can be combined with

-   -   a continuous support on the sleeper head,     -   a dual support on the sleeper head,     -   a triple support on the sleeper head.

In the present embodiment of the invention, the preferred distance between the cross-sleeper axes is 60 cm to 90 cm. Thus, the sleepers have dimensions which make it possible to use the sleepers also in narrow curves and to obtain optimum dissipation of the stresses caused by the running of the vehicle onto the subgrade and in the horizontal extension.

The type of the sleeper construction allows for an enlargement of the sleeper distance such as e.g.

-   -   classical sleeper distance: 600 mm to     -   new attachment distance between the attachment parts: 600 mm+200         mm.

Obtained thereby is, for instance

-   -   at a sleeper distance of 600 mm=1,000.00 m:0.600 m=1,667 sleeper         units/km     -   at 600 mm+200 mm=1,000.00 m:0.80 m=1,250 sleeper units/km.

The widening of the sleeper under the rail does not cause a reduction of the contact surface as compared to the presently used track construction.

The widening of the sleeper under the rail is constructionally optimized with respect to its stability. Herein, for instance, the existing longitudinal connection profile 26 of the bi-block sleeper body 12 is reinforced by an additional steel profile formed as a T-profile or L-profile for use as a reinforcement profile 22 which is oriented at 90° relative to said longitudinal connection profile 26 and is welded thereto. Examples are shown in FIGS. 4 to 7. In the embodiments according to FIGS. 4, 5 and 7, said longitudinal profile 26 is realized as an “upturned” angular profile whereas it is realized as a tube in FIG. 6. As reinforcement profiles, use is made preferably of T-, U- or L-profiles, as illustrated in FIGS. 4 to 7. In this regard, it is essential that these profiles are configured to comprise legs 30 extending at right angles to the rail contact surfaces 18. Said legs 30 either extend in a centered arrangement relative to the rails 24, or (as in the case of the U-profiles of the embodiments according to FIGS. 5 and 6) they extend symmetrically to the central axis of rail 24. In all of these cases, but particularly when using the U-profile arranged with centric orientation relative to the rail in the manner shown in FIGS. 5 and 6, it is achieved that thermally induced expansion/shrinkage of the material below the rail contact surfaces, i.e. below the rails, are substantially prevented because, in this region, the material of the sleeper body is “trapped” or “captured” by the profile element. This is of interest particularly e.g. when using recycled plastic as a material for the sleeper body, or when using other materials having a comparatively high thermal expansion coefficient or a thermal expansion coefficient clearly different from the thermal expansion coefficient of the material of the reinforcement profile elements.

By insertion of iron profiles into free regions in various configurations within the contact area, there is achieved an optimal construction whose statics can be calculated. For this reason, a long useful life can be be expected. However, also other materials can be used for this purpose, such as e.g. plastic (GFK, carbon, Keflar). For protection against corrosion in the exposed central area of the longitudinal (connection) profile 26, use can be made of a PU foam 32, which is illustrated in FIGS. 8 and 9. Said PU foam 32 will adapt to possible thermal expansion movements of the two blocks 14 which may occur if these blocks consist of plastic material. However, the blocks 14 made of e.g. plastic material are held in centered positions by the special reinforcement profiles 22 under the rails 24 so that, in case of a possible thermal expansion of the blocks 14, the rail contact area 16 will not be displaced relative to the rails 24 and will not displace these rails.

A further advantage of the plastic foam 32 is to be seen in that they can be provided with a receiving recess 34 as depicted in FIGS. 8 and 9. Said receiving recess 34 serves for receiving e.g. a conductor rail (not shown).

The material for the blocks 14 consists, on both sides, of recycled plastic. This material is available in large quantities and is important for the further material cycle. By this material, the desired strength is obtained. The material has the following properties which can be used with the aid of controlled processes:

unbreakable temperature-resistant rot-resistant environmentally friendly damping structure-borne noise can be reinforced by glass fibers/ textile fibers or carbon fibers frost-proof UV-stabilized non-ageing dimensionally stable can be armed by steel profiles electrically insulating all of the materials used are reusable

As a result of the decision to use recycled plastic, a wide spectrum for optimizing the material becomes available.

By admixture of granulate from used rubber tires, the vibration is further reduced.

By admixture of steel sinter material, the weight of the rail dampers can be optimized for reduction of lift-off forces.

The coloring of the rail damper can be optimized→e.g. for influencing the temperature or for marking.

Fire-protection can be optimized.

In case of installation within a tunnel, no odor nuisance will occur as caused by impregnated wooden sleepers.

The material is absolutely humidity-resistant.

Long useful life.

Rail-support constructions can be molded into the material.

The material can be sawn, drilled or milled without special tools.

For the first screw connection, no additional dowels need be inserted.

During the period of use of the rail sleepers, no rotting process can occur in the formed screw holes.

The special characteristics of the novel type of rail sleeper are:

-   -   The selection of materials for the sleeper body, including         recyclable plastics.     -   The optimization of plastic as the principle material by         admixture of materials         -   against fire/chemical influences,         -   of granulate from used rubber tires for vibration damping,         -   of steel sinter material for weight optimization,         -   GFK for stabilization etc.     -   The constructional design of the rail contact area by different         welded steel profile inserts and/or plastic inserts.     -   The widened rail sleeper under the rail area, allowing to         provide different rail support structures and different rail         attachment constructions.     -   The constructional design         -   of the double support structure of the rail,         -   of the triple support structure of the rail,         -   of the offset clamping attachment of the rail,         -   of the dual clamping in a sleeper head.

By the present selection of materials, bores for attachment of additional components can be generated in a very simple manner at the most different sites on the sleeper without affecting the statics and the strength of the sleeper. Thus, preferably, the respective inner side of the rails can be provided with a respective derailment-protection angle piece 36 of a suitable dimensioning (see FIG. 8). Said derailment-protection angle pieces 36 have to be provided if the rail sleeper is to be used in derailment-prone sites such as e.g. humps or switchyards.

Since recycled plastic as the material for use herein has properties similar to those of a wooden sleeper and this wooden sleeper is even nowadays still occasionally used on humps and, further, the wooden sleeper is—to a certain extent—prone to cause derailment, the use of the novel rail sleeper in these fields is of particular interest.

Due to the convenient options for shaping the rail sleeper, it is possible to realize special constructions as support structures for

-   -   railroad crossing systems,     -   current rails,     -   green track systems,     -   rail cleaning systems

and other rail construction systems.

The above described features of the novel type of sleeper can also be achieved by use of concrete as a material. In this case, the concrete should be reinforced—in addition to using said steel profile members—by fibers (glass fibers, steel fibers or plastic fibers). Herein, a further reinforcement is to be realized by insertion of a non-prestressed reinforcement. In this construction, the rail attachment screws are to be provided in known plastic dowels which are to be embedded in concrete.

The novel rail sleeper construction makes it possible, in a given load dissipation surface

-   -   to reduce the number of sleepers per rail kilometer,     -   due to the design of the rail contact construction, to reduce         the dynamics caused by the running of the vehicle,     -   to considerably increase the horizontal stiffness of the rail,     -   due to a constructional height equal to that of the wooden         sleeper, to save the costs for lowering the subbase,     -   due to the reduced constructional width in combination with the         horizontal stiffness of the track, to save ballast         volume—ballasting covering only about 30 cm outside the lateral         end of the sleeper.     -   to reduce the emission of structure-borne and air-borne noise,     -   to perform a continuous welding attachment in narrow radii,     -   to take up large braking forces. 

1-10. (canceled)
 11. A rail sleeper comprising a sleeper body comprising respectively a rail contact area on each of its opposing ends and having an enlarged width within said rail contact areas, each rail contact area being adapted for fixation of a rail therein by means of a hold-down element able to engage a rail foot, wherein each rail contact area comprises three rail contact surfaces arranged adjacent to one another in the extension of the rail, at least one hold-down element is arranged between and above at least one partial region of respective adjacent rail contact surfaces of each rail contact area, and the sleeper body is free of reinforcement elements within each rail contact area on both sides of the intermediate spaces between adjacent rail contact surfaces.
 12. The rail sleeper according to claim 11, wherein respectively at least one first reinforcement profile element, extending in the direction of the rail, is arranged below the rail contact areas within the sleeper body.
 13. The rail sleeper according to claim 12, wherein said reinforcement profile is arranged centrally relative to the rail contact area or, in case of two or more reinforcement profiles, these are arranged symmetrically and/or centrically relative to the rail contact area.
 14. The rail sleeper according to claim 12, wherein said reinforcement profile or each reinforcement profile comprises at least one leg extending substantially at a right angle relative to the rail contact area and, in case of a reinforcement profile comprising a plurality of such legs, these legs are arranged symmetrically to the rail contact area.
 15. The rail sleeper according to claim 12, wherein the sleeper body is traversed by at least one second reinforcement profile element which in each of the rail contact areas extends below a middle rail contact surface and which is connected to said first reinforcement profile elements.
 16. The rail sleeper according to claim 12, wherein the sleeper body is configured a bi-block sleeper body comprising two blocks each including one rail contact area, and said first reinforcement profile elements are connected to each other by a second reinforcement profile element, said second reinforcement profile element interconnecting said two blocks and being arranged in each of the rail contact areas below the middle rail contact surfaces.
 17. The rail sleeper according to claim 11, wherein the region of said second reinforcement profile element that is located between said two blocks is protected against corrosion by an enclosure of plastic material.
 18. The rail sleeper according to claim 17, wherein said enclosure of plastic material is formed with a receiving recess for receiving a conductor rail.
 19. The rail sleeper according to claim 11, wherein the sleeper body comprises concrete or polymer concrete.
 20. The rail sleeper according to claim 16, wherein said blocks comprise plastic and/or said second reinforcement profile element and optionally also said first reinforcement profile elements comprises a substantially plane surface. 